Dietary vitamin E alleviates ammonia-induced effects on survival, anti-oxidant and immune response of post-larval Pacific white shrimp.
It remains unknown whether vitamin E (VE), a fat-soluble vitamin known for its potent antioxidant effects, alleviates the stress caused by ammonia-N exposure in post-larval Pacific white shrimp (Penaeus vannamei). Five isonitrogenous (crude protein: 32.5%) and isolipidic (crude lipid: 9.22%) diets were formulated containing DL-α-tocopheryl acetate at concentrations of 0, 40, 80, 120 and 160 mg/kg (E13.1, E50.6, E90.5, E130.6 and E163.9, respectively). Post-larval P. vannamei individuals (3.95 ± 0.21 mg) were randomly assigned to 20 tanks and fed the experimental diets for 34 days. After the feeding trial, the shrimp were challenged with ammonia-N for 48 h to evaluate their stress tolerance and immune responses. The shrimp groups fed with diet supplemented with VE exhibited significantly improved growth performance and feed utilization compared to the E13.1 group (P < 0.05). However, dietary VE levels had no significant effect on survival (P > 0.05). Dietary VE supplementation increased LT50 from 36 h in the E13.1 group to 48 h in the E90.5 group. Dietary VE supplementation significantly upregulated the expression of antioxidant-related (SOD, CAT and GPx) and immune-related (Crustin, proPO, HSP70 and Penaeidin-3a) genes both after the feeding trial (0 h) and after ammonia-N exposure (48 h) (P < 0.05). Optimal dietary VE levels estimated using broken-line and second-order polynomial regression analyses ranged from 89.3 to 94.9 mg/kg for growth and 82.6 to 113.9 mg/kg for ammonia-N stress resistance in post-larval P. vannamei. Overall, these findings indicate that dietary VE mitigates acute ammonia-N induced damage in shrimp by enhancing antioxidant defense and immune responses.